Chapter 22. JXPath

Overview

The JXPath language enables you to invoke Java beans using the Apache Commons JXPath language. The JXPath language has a similar syntax to XPath, but instead of selecting element or attribute nodes from an XML document, it invokes methods on an object graph of Java beans. If one of the bean attributes returns an XML document (a DOM/JDOM instance), however, the remaining portion of the path is interpreted as an XPath expression and is used to extract an XML node from the document. In other words, the JXPath language provides a hybrid of object graph navigation and XML node selection.

Adding JXPath package

To use JXPath in your routes you need to add a dependency on camel-jxpath to your project as shown in Example 22.1, “Adding the camel-jxpath dependency”.

Example 22.1. Adding the camel-jxpath dependency

<!-- Maven POM File -->
<properties>
  <camel-version>2.21.0.fuse-730078-redhat-00001</camel-version>
  ...
</properties>

<dependencies>
  ...
  <dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-jxpath</artifactId>
    <version>${camel-version}</version>
  </dependency>
  ...
</dependencies>

Variables

Table 22.1, “JXPath variables” lists the variables that are accessible when using JXPath.

Table 22.1. JXPath variables

VariableTypeValue

this

org.apache.camel.Exchange

The current Exchange

in

org.apache.camel.Message

The IN message

out

org.apache.camel.Message

The OUT message

Options

Table 22.2, “JXPath option” describes the option for JXPath.

Table 22.2. JXPath option

OptionTypeDescription

lenient

boolean

Camel 2.11/2.10.5: Allows to turn lenient on the JXPathContext. When turned on this option allows the JXPath expression to evaluate against expressions and message bodies which might be invalid or missing data. See more details at the JXPath Documentation. This option is false, by default.

Examples

The following example route uses JXPath:

<camelContext>
  <route>
    <from uri="activemq:MyQueue"/>
    <filter>
      <jxpath>in/body/name = 'James'</xpath>
      <to uri="mqseries:SomeOtherQueue"/>
    </filter>
  </route>
</camelContext>

The following simple example uses a JXPath expression as a predicate in a Message Filter:

{snippet:id=example|lang=java|url=camel/trunk/components/camel-jxpath/src/test/java/org/apache/camel/language/jxpath/JXPathFilterTest.java}

JXPath injection

You can use Bean Integration to invoke a method on a bean and use various languages, such as JXPath, to extract a value from the message and bind it to a method parameter.

For example:

public class Foo {
     @MessageDriven(uri = "activemq:my.queue")
     public void doSomething(@JXPath("in/body/foo") String correlationID, @Body String body)
     { // process the inbound message here }
   }

Loading the script from an external resource

Available as of Camel 2.11

You can externalize the script and have Camel load it from a resource such as "classpath:", "file:", or "http:". Use the following syntax:

"resource:scheme:location"

For example, to reference a file on the classpath:

.setHeader("myHeader").jxpath("resource:classpath:myjxpath.txt")